Expansive cement and its method of manufacture

ABSTRACT

A method of preparing an expansive cement having a controlled expansion and the same workability as normal Portland cement and the cement so prepared.

AU 115 Ex United States Patent 1 Deets et al. 1 Jan. 21, 1975 [54] EXPANSIVE CEMENT AND ITS METHOD 3,251,701 5/1966 Klein 106/89 OF 3111221 11:22; [75] Inventors; John L. Deets, Griffith, Calument 3:5 0:32 5 1970 Township; Zvonimir T. ]ug0vic, 3,775,143 11/1973 Mikhailov et al 1116/89 xlnster, North Township, both of OTHER PUBUCATONS Blanks; Robert F., The Technology of Cement and [73] Amgneegqz zt si Concrete, Vol. l. Wiley & Sons. NY. 1955. pp.

S g 40-42. [22] Filed: Oct. 27, 1972 Mikhailov, V. V.. Stressing Cement." Fourth Interna- 1 1 ppl. No.: 301,382 g g ggg 5 g g g g y of Cement.

Related US. Application Data [63] Continuation-impart of Ser. No. 172,691, Aug. 18, Primary Examiner-Delbert E. Gantz 1971, abandoned. Assistant Examiner-James W. Hellwege [52] U S Cl 106,89 106/104 106,109 Attorney, Agent, or FirmRalph H. Dougherty [51] Int. Cl. C041) 7/02, C04b 7/04 7 TRACT [58] Field of Search 106/89, 314, 104, 109 [5 1 A method of preparing an expansive cement having a [56] References Cited controlleld expansion and t1llle same workability as nor- UNITED STATES PATENTS mal Port and cement and t e cement so prepared. 3.215549 11/1965 Ericson 106/90 4 Claims. 4 Drawing Figures PATENTED JANZI I975 SHEEI 10F 2 EXCESS so,

FIG. 2.

.WNQQQQU 7'/ME IN DAYS TIME /N DAYS PATENTEDJANZI ms SHEEI 2 OF 2 FIG. 4.

sxcsss so,

EXPANSIVE CEMENT AND ITS METHOD OF MANUFACTURE REFERENCE TO RELATED APPLICATION This is a continuation-in-part application of our ap- 5 expansive potential, has, in preparation of the conplication Ser. No. 172,691, filed Aug. 18, 1971 now abandoned.

BACKGROUND OF THE INVENTION Because ofthe low tensile strength of the cured material, the inherent shrinkage characteristics of concretes made with conventional cements cause cracks on hardening and drying. Efforts have been made to overcome these weaknesses by various mechanical means, such as pre-stressing or post-stressing; however, such methods often require elaborate techniques and equipment. Efforts have also been made to produce cement which, when mixed with water, will expand and thereby compensate, to some degree or entirely, for the usual shrinkage of Portland cement concrete.

Expansive cement is a cement which, when mixed with water, forms a paste that, during and after setting and hardening, increases significantly in volume. Shrinkage-compensating concrete, mortar or grout is an expansive cement concrete, mortar or grout, in which expansion, if restrained, induces compressive stresses which approximately offset tensile stresses in the concrete induced by drying shrinkage. Selfstressing concrete, mortar or grout is an expansive cement concrete, mortar or grout, in which expansion is 3 restrained inducing compressive stresses of a high enough magnitude to result in a significant compression in the concrete after drying shrinkage has occurred.

In most of the expansive cement formulations, the formation ofettringite (3CaO.Al O -;.3CaSO..32H2O) is the source of the expansive force. Early investigators ofettringite in cement recognized the potential of using this compound for inducing stresses on reinforcing steel, thus developing, during the curing period, a slight compression in the concrete. It is desirable to have sufficient initial compression in the concrete to prevent the development of tensile stress during the drying period, thus increasing its crack resistance. The development and the properties of various expansive cements have been described in many publications and are summarized in the report of ACI Committee 223 entitled, Expansive Cement Concretes Present State of Knowledge published in the Journal of the American Concrete Institute, Vol. 67, No. 8, Aug., 1970, pp. 583-610.

Although many investigators in various countries have discovered ways of producing expansive cements, most of these were not commercially made because of inability to reproduce the cements with reliable properties as well as due to complications in the technology of manufacture. Non-shrinking and self-stressing expansive cements as produced heretofore have had some or all of the following disadvantages:

1. short workability time in concrete as compared to normal Portland cement in concrete;

2. the necessity of special precautions during the curing period of conceret;

3. limited storage time the expansive potential deteriorates with age;

4. the necessity of control agents for limiting the rate and the magnitude of expansion; and

crete, the same workability characteristics as any normal Portland cement concrete.

It is also an object of this invention to provide an expansive cement for shrinkage compensating concrete. mortar or grout which needs no special curing or precautions other than those normally recommended for any quality Portland cement concrete.

SUMMARY OF THE INVENTION- We have discovered that relatively small amounts of calcium aluminate cement or clinker, about 2 to 17 pmhemfh wmr clinker, and calcium sulfate expressed as percent excess S0,, over optimum S0 determined according to ASTM Stand- 20 ard C563-70 and equal to about 2 to 24 percent, when thereby insure manufacture of cement with consistent properties. This is of particular importance for the relatively low levels of expansive potential of a cement used in shrinkage-compensating concrete.

Our improved expansive cement composition, consisting of Portland cement or clinker, calcium aluminate cement or clinker and calcium sulfate has the following improved properties:

I. The workability, placement, compaction and finishing characteristics, all at normal water requirements witth no excessive slump loss, are equal to those of a normal Portland cement concrete.

2. The amount of expansion of the particular formulation can be readily controlled and duplicated making it applicable to special field requirements.

3. The curing of shrinkage-compensating concrete is subject to only those precautions commonly recognized for curing ordinary concrete in hot or cold weather.

4. The expansive potential of the shrinkagecompensating concrete is optimized in a relatively short curing period of 3-4 days.

5. Storage requires no limitations in time or facilities other than those recommended for normal Portland, calcium aluminate, or any other hydraulic cement.

6. Manufacture requires no special expansive components but uses. commercially produced hydraulic cements or clinkers (Portland and calcium aluminate) and calcium sulfate.

7. The strengths of mortars or concrete are equal to or better than those obtained with regular Portland cement mortar or concrete when suitable restraint is used.

8. The cement can be produced by either intergrinding, blending or a combination of grinding and blending of said components in the proportions recommended for specific range of expansive characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a graph of the percent expansion of a concrete using a cement of our invention plotted against the excess 50;, over optimum S determined according to ASTM Standard C563-70. The results shown are for a composition containing 5.5 weight percent,

composition are ground to final size prior to blending, we prefer to use calcium sulfate dihydrate (gypsum). Where the components of our cement are combined before grinding to final size. we prefer to limit the dihybased on the total composition, of low iron (less than 5 drate form to a maximum of about weight percent 2.5% as Fe O calcium aluminate cement cured in a based on the total composition. Any calcium sulfate rehot water bath (145F) until not further expansion quirement over 10 weight Peroeht is preferably met y was notgd (under 24 hours) Th percent t i t the addition of anhydrous calcium sulfate. Calcium sulwas fate in hemihydrate form (CaSO .%H O) should be Fit}. 2 is a graph of the compressive strength of a to present in our cement product in an amount from mortar using a cement of our invention plotted against about 2 to 8 Porooht y Weight of the final expansive time cement composition, and preferably will not exceed 60 FIG 3 is a graph of the percent expansion ofa mortar percent of the totaicalcium sulfate present in the comusing a cement of our invention plotted against time. in Posmohh hemlhtfdrate deslrable for control of both H65. 2 and 3, based on the total composition, the early hydranoh reacuohslow iron calcium aluminate cement was 5.6 weight per- The f ll wi bl summarizes h proportions f cent and the percent excess SO; over optimum was the above constituents of our composition which result 2.4. P rcent restraint was 0.36. The cement mortar in concretes having the beneficial results of our invenwas cured at 73F for the period of the test. ti

Table l Useable Range Preferred in Parts Range in Parts Shrinkage- Self- Shrinkage- Self- Component Compensation Stressing Compensating Stressing Calcium Aluminate Cement or Clinker 2l7 3.5-l7 2-9 6-17 Excess SO, (added in the forms of calcium sulfate) 2-24 6-24 3-1 l 9-24 Portland Cement or Clinker 100 100 too too FIG. 4 is a graph of the percent mortar expansion The calcium aluminate cement or clinker content of plotted against the excess S0 over optimum for two our composition must be kept above about 2 weight cements of our invention containing different calcium percent to obtain any expansion. When the calcium aluminate cements and different quantities of calcium aluminate cement or clinker is above 17 weight peraluminate cement. The expansion was determined after nt it y set too q k yn the ss 03 Over three days of curing at 73F. Percent restraint was 0.36. optim m iS be o 2 eight percent, there is insufficient Curve A is that of mortar made with a cement contain- E P O when the eXoeSS 3 over optimum i5 ing 5.6 weight percent calcium aluminate cement havabove about 24 weight percent, the strength of the ing an iron content of about 2 to 2.5 percent as F6203. concrete may be adversely affected. Curve B is that of mortar made with a cement contain- The Procedure for p p g the Controlled P i 2 i h percent f a very l i b 1% sive cementofour invention is as follows. The first step F 0 l i l i t m, is to determine the optimum 80;; of the particular Portland cement clinker to be used in the com osition. DETAILED. DESCRIPTION The procedure followed is set forth in ASTM S tandard The controlled expansive cement of our invention is prepared from a mixture of Portland cement orclinker, Once the optimum $03 of the particular Portland calcium. aluminate Cement or Chnker and mentor clinker is determined, a calcium aluminate cef wh'ch has been grouhd and blehded to homogene' ment or clinker level is selected in the range of from 'Y- h cement chhker wh'ch wouki P o about 2 to about 17 percent by weight of the Portland a cement meeting M Standard C150'70 f cement. When a shrinkage-compensating cement is to for use our Composition Preferablyi the P be prepared, the calcium aluminate cement or clinker strength potential at the optimum SO level of the chnshould be in the range of from about 2 to about 17 ground lhto a Portland Cement o tested b cent, preferably from about 2 to about 9 percent. When ASTM Standard C563 i5 emu/6.3.600 P The a self-stressing cement is to be prepared, the calcium kor t5 Produced y cohYohtlohal fhethodsaluminate cement or clinker should comprise from Nor are Special calcium aluminate cements h about 3.5 to about 17 weight percent, preferably from 'yy Calcium aluminate cement or chhkbf about 6 to about 17 weight percent. Additional quantiabie for use in out composition with the Proviso only ties of 80;, are then added to different batches of that the maximum iron Content expressed as zoa Portland cement-calcium aluminate cement mixtures the Cement Clinker not exceed about 20 Percent, and the expansion at each S0 level determined. The preferably not exceeding about 5 p The ohhkel' results are then plotted on a graph such as that shown or cement is produced by conventional methods.

The calcium sulfate may be added to our cement either in hydrous forms or in anhydrous and hydrous forms together. It may be added in mineral form, preferably as gypsum. When the three components of our in FIG. 1 using restraint systems and curing conditions suitable for the proposed ultimate use. The results will vary depending on the amount of calcium aluminate cement present in the mixture and also on the particular calcium aluminate cement used. The expansion occasioned by the excess 80;; may then be determined at different calcium aluminate cement levels and the composition having the desired rate of expansion and strength characteristics is chosen. Once the effect of different levels ofexcess 50;; has been plotted. it is only necessary to add the same quantity of excess S0 to subsequent batches of cement to obtain the same expansion. Thus, when a cement is to be prepared from a new batch of Portland cement clinker. the optimum S03 is determined according to ASTM Standard C563-70, the predetermined amount ofcalcium aluminate cement or clinker is added and the excess 50;, level necessary for the desired expansion is determined by reference to a graph comparable to FIG. 1. We have found that in preparing shrinkage-compensating cements, the excess 50:, level should be in the range of about 2 to 24 weight percent, preferably about 3 to 1 1 weight percent. When preparing a self-stressing cement, the excess 50;; level should be in the range of about 6 to 24 weight percent, preferably about 9 to 24 weight percent of the Portland cement.

Once the proportions of the three constituents of our composition have been chosen by the above method they are combined to form a controlled expansive cement having the desired expansion level. The constituents may be combined and then interground or the constituents may be ground separately and then blended to form the cement.

When the cement is to be prepared by intergrinding the components, the proper proportions are selected and fed to the grinding mill. We prefer to limit the amount of S0 equivalent obtained from calcium sulfate dihydrate (gypsum) to a level of about weight percent of the total composition. If an additional quantity of calcium'sulfate is necessary to provide the desired 80;, level. we prefer to add the calcium sulfate in. the anhydrous form provided sufficient hemihydrate is present in the composition. The constituents are ground by conventional means to meet the fineness requirements of ASTM Standard Cl50-70 as tested by ASTM Standard Cl -70.

In a preferred method, the constituents of our composition are first separately ground and then blended in any conventional manner. The calcium aluminate cement constituent should be ground to a Wagner surface about about 1,350 cm lgm, preferably above about 1,400 cm /gm. The Portland cement clinker should be ground to a Wagner surface above about 1,600 cm /gm, preferably above about 1,800 cm /gm. The Portland cement clinker may be ground with an amount of gypsum that will provide the optimum 50;, content as determined by ASTM Standard C56370. The calcium sulfate, preferably in the dihydrate form, should be ground to a point where at least 70 percent will pass a No. 100 sieve (USA Standard) and preferably to a point where at least 85 percent will pass a No. 100 sieve. After grinding, the required proportions of each constituent are blended. If no gypsum or an insufficient amount of gypsum is ground with the Portland cement clinker to provide at least 2 percent hemihydrate in the final expansive cement composition, sufficient calcium sulfate in the hemihydrate form should be added to provide this minimum.

Although our novel process and cement have been described in terms of Portland cement or clinker, it should be understood that other cements or clinkers may be substituted for the Portland cement or clinker.

LII

10 parative techniqes useful in practicing our invention.

They should of course be taken as being merely illustrative and not limiting in any way.

EXAMPLE 1 A shrinkage-compensating expansive cement was prepared from 86.3 parts by weight nd cement clinker, 5.6 parts by weight low iron content calcium aluminate cement clinker and 8.1 parts by weight CaSELZH O equivalent to 3.6 parts by weight S03.

hmfifif'so, level of the Portland cement clinker was determined using ASTM Standard C563- as 1.7 percent. The expansive cement was prepared by intergrinding the components in a laboratory mill to a Wagner surface of 1,900 cm /gm. The expansion of this ce- 25 ment was measured on 2X2 l0 inches restrained mortar prisms using a length comparator conforming with that described in ASTM Standard C490-70. The mortar mix consisted of the cement and graded Ottawa sand in a 112.75 mix by weight with sufficient water to provide a flow of l00l 15 percent comparable with ASTM Standard Cl0964. Mixing was done in accordance with ASTM Standard C30565. The molds were of such dimensions as to provide sufficient space to insert a restraining cage consisting of a 3/16 inch diameter threaded mild steel rod having an overall length of 11-9/16 inch i l/l6 inch and two mild steel end plates 2 2 3/8 inch. The end plates were positioned on the rod to provide a 10 inch opening between them and were secured in this position with locknuts. The steel cages were assembled and measured for length in the comparator prior to insertion in the mold. Subsequent measurements were referred to this initial measurement. Molded specimens were placed in the moist cabinet (73 3F, i percent relative humidity)-for S-B hours, demolded and then placed in saturated lime water (73 3F) until completion of the test. At the conditions as set forth above, the percent expansion after three days was 0.077 percent and after 7 days, 0.078 percent. The compressive strength determined in accordance with ASTM Standard Cl09-64 was 2,950 psi (3 day) and 4,270 psi (7 day).

EXAMPLE 2 The procedure of Example 1 was followed using a Portland cement prepared from 83.8 parts by weight Portland cement clinker, 5.6 parts by weight low iron content calcium aluminate cement clinker, and 10.6 parts by weight CaSO4.2H O (equivalent to 4.7 parts by weight S03). The Portland cement had an optimum 50;, level of 2.6 percent. The 3-day expansion of this cement composition was 0.091 percent and the 7-day expansion was 0.087 percent. Compressive strengths were 3,080 psi (3 day) and 4,230 psi (7 day).

EXAMPLE 3 A shrinkage-compensating expansive cement was prepared from 85.6 parts by weight Portland cement v v x aluminate clinker, 6.0 parts by weight low iron content calcium cement clinker, 5.3 parts by weight caso..2H.o equivalent to 2.3 parts by weight S03. and 3.] parts by weight caso.. /2H.o equivalent to L7 parts by weight S The optimum SO, level of the Portland cement clinker was L8 percent. The expansive cement was prepared by intergrinding the components in a laboratory mill to a Wagner surface of L890 cm-'/g. The 3-day expansion of could be conveniently used in a length comparator conforming to the type described in ASTM Standard C49070 The length of the longitudinal restraining rod was measured prior to molding the specimens. All later measurements were referred to this initial measurement. The specimens were cured in a hot water bath, held at l450F until no further expansion was noted. This occurred within 24 hours. The percent expansion and the calculated compressive stress based on this cement composition was 0.089 percent and the 19 the yield Strength of the Stee' are listed in Table Table III Composition in Parts Calcium Portland Aluminate Cement Cement Excess SO; Ce- Clinker Clinker Gypsum Anhydrite weight percent ment lron Content less than 2.5% as Fe,0, Gypsum 44.5% 50, Anhydrite 55.5! 50,

7-day expansion was 0.093 percent. Compressive Table IV strengths were 1,950 psi (3 day) and 3.780 psi (7 day). Cement Expansion. '71 Calc. Compressive Stress. psi

Table ll a comparison of cement compositions of Examples 1. 2 and 3. It shows that the percent expansion of the three cement compositions having approxi- 3O 3 0.220 127 mately equal excess 80;; is approximately equal. it is therefore apparent that the procedure of this invention makes it possible to control both the magnitude and We Claimi rate of expansion of the expansive cement composition. 1. The method of controlling the degree of expansion Selfstressing concrete mixes were prepared composed of 8 sacks of cement (94 lbs. each) per cubic yard of concrete, a water to cement ratio equal to 0.517 by weight, and a mixture of concrete sand meeting ASTM C33-67 specifications for fine aggregates and a commercially prepared lightweight aggregate of expanded crushed shale having a maximum size of one half inch where the sand constituted 74 percent of the total aggregate by weight, or 37 percent by volume.

Three different cement compositions were prepared having the proportions listed in Table Ill. Prisms having a cross sectional shape of 3X3 inches and a length of 10 inches were cast from each concrete mix. Each prism was provided with a longitudinal restraining rod fabricated from high strength stainless steel (No. 431) with a diameter of 0.274 inch. The effective gauge length of the rod between the end plates was 10 inches. Overall length of the rod was ll Y4 inches. Lateral reinforcement consisted of six squares of 12 gauge 2X2 inch mesh equally spaced throughout the length of the specimen The longitudinal rod had ends of a design which of an expansive cement comprising adding a quantity of calcium sulfate to a mixture consisting essentially of Portland and calcium aluminate cements or clinkers, said calcium aluminate cement being present in an amount from about 2 to 17 weight percent of the Portland cement. to provide an excess of 80:: over the optimum S0 of about 2 to 24 weight percent of the Portland cement, said optimum being determined in accordance with ASTM Standard C563- with said excess of 503 being sufficient to give a cement having the desired expansion level.

2. The method of claim 1 wherein about 2 to 8 weight percent of the expansive cement composition is CaSOfl/zl-LO.

3. The method of claim 2 wherein the calcium sulfate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the composition.

4. The method of claim 1 wherein the calcium sulfate is added in the form of gypsum.

5. The method of claim 1 wherein the expansive cement is a shrinkage-compensating cement, the calcium aluminate cement is about 2 to 9 weight percent. and the excess of S03 is about 3 to l l weight percent of the Portland cement.

6. The method of claim 1 wherein the expansive cement is a self-stressing cement, the calcium aluminate cement or clinker is about 3.5 to 17 weight percent and the excess of S0,; is about 6 to 24 weight percent of the Portland cement or clinker.

7. The method of claim 1 wherein the expansive cement is a self-stressing cement, the calcium aluminate cement or clinker is about 6 to 17 weight percent, and the excess of S03 is about 9 to 24 weight percent of the Portland cement or clinker.

8. The method of claim I wherein calcium sulfate is added as gypsum up to about l weight percent of the total composition and the remainder of the calcium sulfate required to give said excess of $0 over the optimum S01. is added as anhydrous calcium sulfate.

9. The method of reproducing the expansion level of a first expansive cement in a second expansive cement comprising determining the excess of $0 over the optimum S0,, in said first expansive cement and adding a quantity of calcium sulfate to a second expansive cement sufficient to give that same excess of $0 over the optimum $0 in said second expansive cement where:

a. the optimum S0 is determined in accordance with ASTM Standard C563-7:

b. the expansive cements consist essentially of Portland cement. calcium aluminate cement, and calcium sulfate;

c. the amount and type of calcium aluminate cement is the same in said first expansive cement and said second expansive cement; and

d. the excess of S0 over the optimum S0 is in the range of 2 to 24 weight percent-and the calcium aluminate cement is in the range of 2 to 17 weight percent of the Portland cement.

10. The method of claim 9 wherein about 2 to 8 weight percent of the expansive cement composition is CaSO4. /2H O.

11. The method of claim wherein the calcium sulfate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the composition.

12. The method of claim 9 wherein the expansive cement is a shrinkage-compensating cement, the calcium aluminate cement is about 2 to 9 weight percent and the excess S03 is about 3 to ll weight percent of the Portland cement.

13. The method of claim 9 wherein the expansive cement is a self-stressing cement, the calcium aluminate cement is about 3.5 to 17 weight percent and the excess 80;, is about 6 to 24 weight percent of the Portland cement.

14. The method of claim 9 wherein the expansive cement is a self-stressing cement, the calcium aluminate cement is about 6 to 17 weight percent and the excess 80;, is about 9 to 24 weight percent of the Portland cement.

15. The method of claim 9 wherein the calcium sulfate is added as gypsum.

16. The method of claim 9 wherein the components are combined before grinding to final size, in which the calcium sulfate is added as gypsum to a maximum of about 10 weight percent of the total composition and the remainder of the calcium sulfate required to give the determined excess of $0 over the optimum S0 is added as anhydrous calcium sulfate.

17. The process for preparing a cement having controlled expansive properties consisting essentially of Portland cement, calcium aluminate cement in the amount from about 2 to 17 weight percent of the Portland cement, and calcium sulfate to provide excess 50;; over the optimum 50;; of about 2 to 24 weight percent of the Portland cement, said optimum being determined by ASTM Standard C563-70 comprising:

a. determining the optimum 80;, for the Portland cement.

b. grinding the Portland cement constituent to an average minimum Wagner surface of at least 1,600 cm /gm,

c. grinding the calcium aluminate cement constituent to an average minimum Wagner surface of at least L350 cm /gm.

d. grinding the calcium sulfate so that at least percent passes through a No. 100 sieve. and

e. blending to homogeneity the Portland cement and the calcium aluminate cement with a sufficient excess of S03 over the optimum S0 determined in step (a). added as calcium sulfate to give a cement having the desired expansion level.

18. The process of claim 17 wherein the calcium sulfate is ground so that at least percent'passes through a No. sieve.

19. The process of claim 17 wherein the calcium sulfate is added in the form of gypsum.

20. The process of claim 17 wherein the cement is a shrinkage-compensating cement, the calcium aluminate cement is about 2 to 9 weight percent of the Portland cement and the excess S0 is about 3 to l 1 weight percent of the Portland cement.

21. The process of claim 17 wherein the cement is a self-stressing cement, the calcium aluminate cement is about 3.5 to 17 weight percent of the Portland cement arid the excess S03 is about 6 to 24 weight percent of the Portland cement.

22. The process of claim 17 wherein the cement is a self-stressing cement, the calcium aluminate cement is about 6 to 17 weight percent of the Portland cement andthe excess 50;; is about 9 to 24 weightpercent of the Portland cement.

23. The process of claim 17 wherein 2 to 8 weight percent of the cement is CaSO4. /H- O.

24. The process of claim 23 wherein the calcium sul fate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the cement.

25. The process of claim 17 wherein the Portland cement is replaced by a blended hydraulic cement selected from Portland blast furnace slag cements and Portland Pozzolan cements meeting ASTM Standard C595-68.

26. The process for preparing a cement having controlled expansive properties consisting essentially of Portland cement clinker, calcium aluminate cement clinker in the amount from about 2 to 17 weight percent of the Portland cement clinker, and calcium sulfate to provide excess S0 over the optimum S0 of about 2 to 24 weight percent of the Portland cement clinker, said optimum being determined by ASTM Standard C563-7O comprising:

a. determining the optimum S0 for the Portland cement clinker,

b. mixing the Portland cement clinker and calcium aluminate cement clinker with a sufficient excess of S03 over the optimum S0 determined in step a. added as calcium sulfate to give a cement having the desired expansion level. and

c. grinding the mixture to an average minimum Wagner surface of 1,600 cm /gm.

27. The process of claim 26 in which the calcium sulfate is added as gypsum to a maximum of about 10 weight percent of the total composition and the rcmainder of the calcium sulfate required to provide the determined excess of $0 over the optimum S() is added as anhydrous calcium sulfate.

28. The process of claim 26 wherein 2 to 8 weight percent of the cement is CaSO4. /2H O.

29. The process of claim 28 wherein the calcium sulfate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the cement.

30. The process of claim 26 wherein the cement is a shrinkage-compensating cement, the calcium aluminate cement clinker is about 2 to 9 weight percent of the Portland cement clinker and the excess 80;, is about 3 to ll weight percent of the Portland cement clinker.

31. The process of claim 26 wherein the cement is a self-stressing cement, the calcium aluminate cement clinker is about 6 to 17 weight percent of the Portland cement clinker and the excess 50;; is about 9 to 24 weight percent of the Portland cement clinker.

32. The process of claim 26 wherein the Portland cement clinker is replaced by a blended hydraulic cement selected from Portland blast furnace slag cements and Portland Pozzolan cements meeting ASTM Standard C595-68.

33. An expansive cement having controlled expansive properties consisting essentially of Portland cement, calcium aluminate cement in an amount from about 2 to 17 weight percent of the Portland cement, and calcium sulfate to provide excess 50;, over the optimum 50;; of about 2 to 24 weight percent of the Portland cement, said optimum being determined by ASTM Standard C563-70.

34. The expansive cement of claim 33 wherein the calcium sulfate is added in the form of gypsum.

35. The expansive cement of claim 33 wherein about 2 to 8 weight percent of the cement is CaSO4JH O.

36. The expansive cement of claim 35 wherein the calcium sulfate present in hemihydrate form is no greater than percent of the total calcium sulfate in the cement.

37. The expansive cement of claim 33 wherein said cement is a shrinkage-compensating cement. the calcium aluminate cement is about 2 to 9 weight percent of the Portland cement and the excess S0 is about 3 to l 1 weight percent of the Portland cement.

38. The expansive cement of claim 33 wherein said cement is a self-stressing cement, the calcium aluminate cement is about 3.5 to 17 weight percent of the Portland cement and the excess 50;, is about 6 to 24 weight percent of the Portland cement.

39. The expansive cement of claim 33 wherein said cement is a selfstressing cement, the calcium aluminate cement is about 6 to 17 weight percent of the Portland cement and the excess S0 is about 9 to 24 weight percent of the Portland cement.

40. The expansive cement of claim 33 wherein the Portland cement is replaced by a blended hydraulic cement selected from Portland blast furnace slag cements and Portland Pozzolan cements meeting ASTM Standard C595-68.

I UNITED STATES PATENT OFFICE M0 A 9 Patent No.

lnventol-(s) John L. Beets et 2.1.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title Page at "Calument" should read Calumet Column v line 5 "mncemt" should read concrete Column 3, line 18, P ICQKTTL" sawld read Percent Colum. 6, line 4 $0 perce should read 520 percento 1 Column line '5, "1 50 F" should ream. l -;:F

:T' -olu-"wn J, line 7.), "C5i55-7" should read (3565-70 Signed and sealed this 17th day of June 1975.

SEAL) Attest C. I ARSHALL DANN RUTH C. I-ASON Commissioner of Patents Arresting Officer and Trademarks F ORA POIOSO SIQEQ) A uscoMM-oc 60376-'P69 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO 5,861,929 January 21, 19575 Dated lnventofls) John L. Beet-s et :11,

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Page at "Caloment" should read Calumet Column 1 line so, "mosey-Ti" should read. oonor'ete Colman 3, lime .L

, "F ICZYEIH Lho'afld Percent Colunm 6, line M $730 peroewt sr'xoulxi rear percent o I M. Golunm line "l -4390 F should 1 211:")?

:Jolmm line 151-, "fiiiil'ii-ll" should read, (35-53-79 Signed and sealed this 17th day of June 1975.

Attest- C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks F ORM PO-105G (10-69) USCOMM-DC 60376-P69 u s rmvzwmzm PRINTING ervlcaz 865* 930 

2. The method of claim 1 wherein about 2 to 8 weight percent of the expansive cement composition is CaS04. 1/2 H20.
 3. The method of claim 2 wherein the calcium sulfate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the composition.
 4. The method of claim 1 wherein the calcium sulfate is added in the form of gypsum.
 5. The method of claim 1 wherein the expansive cement is a shrinkage-compensating cement, the calcium aluminate cement is about 2 to 9 weight percent, and the excess of S03 is about 3 to 11 weight percent of the Portland cement.
 6. The method of claim 1 wherein the expansive cement is a self-stressing cement, the calcium aluminate cement or clinker is about 3.5 to 17 weight percent and the excess of S03 is about 6 to 24 weight percent of the Portland cement or clinker.
 7. The method of claim 1 wherein the expansive cement is a self-stressing cement, the calcium aluminate cement or clinker is about 6 to 17 weight percent, and the excess of S03 is about 9 to 24 weight percent of the Portland cement or clinker.
 8. The method of claim 1 wherein calcium sulfate is added as gypsum up to about 10 weight percent of the total composition and the remainder of the calcium sulfate required to give said excess of S03 over the optimum S03 is added as anhydrous calcium sulfate.
 9. The method of reproducing the expansion level of a first expansive cement in a second expansive cement comprising determining the excess of S03 over the Optimum S03 in said first expansive cement and adding a quantity of calcium sulfate to a second expansive cement sufficient to give that same excess of S03 over the optimum S03 in said second expansive cement where: a. the optimum S03 is determined in accordance with ASTM Standard C563-70; b. the expansive cements consist essentially of Portland cement, calcium aluminate cement, and calcium sulfate; c. the amount and type of calcium aluminate cement is the same in said first expansive cement and said second expansive cement; and d. the excess of S03 over the optimum S03 is in the range of 2 to 24 weight percent and the calcium aluminate cement is in the range of 2 to 17 weight percent of the Portland cement.
 10. The method of claim 9 wherein about 2 to 8 weight percent of the expansive cement composition is CaS04. 1/2 H20.
 11. The method of claim 10 wherein the calcium sulfate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the composition.
 12. The method of claim 9 wherein the expansive cement is a shrinkage-compensating cement, the calcium aluminate cement is about 2 to 9 weight percent and the excess S03 is about 3 to 11 weight percent of the Portland cement.
 13. The method of claim 9 wherein the expansive cement is a self-stressing cement, the calcium aluminate cement is about 3.5 to 17 weight percent and the excess S03 is about 6 to 24 weight percent of the Portland cement.
 14. The method of claim 9 wherein the expansive cement is a self-stressing cement, the calcium aluminate cement is about 6 to 17 weight percent and the excess S03 is about 9 to 24 weight percent of the Portland cement.
 15. The method of claim 9 wherein the calcium sulfate is added as gypsum.
 16. The method of claim 9 wherein the components are combined before grinding to final size, in which the calcium sulfate is added as gypsum to a maximum of about 10 weight percent of the total composition and the remainder of the calcium sulfate required to give the determined excess of S03 over the optimum S03 is added as anhydrous calcium sulfate.
 17. The process for preparing a cement having controlled expansive properties consisting essentially of Portland cement, calcium aluminate cement in the amount from about 2 to 17 weight percent of the Portland cement, and calcium sulfate to provide excess S03 over the optimum S03 of about 2 to 24 weight percent of the Portland cement, said optimum being determined by ASTM Standard C563-70 comprising: a. determining the optimum S03 for the Portland cement, b. grinding the Portland cement constituent to an average minimum Wagner surface of at least 1,600 cm2/gm, c. grinding the calcium aluminate cement constituent to an average minimum Wagner surface of at least 1,350 cm2/gm, d. grinding the calcium sulfate so that at least 70 percent passes through a No. 100 sieve, and e. blending to homogeneity the Portland cement and the calcium aluminate cement with a sufficient excess of S03 over the optimum S03 determined in step (a). added as calcium sulfate to give a cement having the desired expansion level.
 18. The process of claim 17 wherein the calcium sulfate is ground so that at least 85 percent passes through a No. 100 sieve.
 19. The process of claim 17 wherein the calcium sulfate is added in the form of gypsum.
 20. The process of claim 17 wherein the cement is a shrinkage-compensating cement, the calcium aluminate cement is about 2 to 9 weight percent of the Portland cement and the excess S03 is about 3 to 11 weight peRcent of the Portland cement.
 21. The process of claim 17 wherein the cement is a self-stressing cement, the calcium aluminate cement is about 3.5 to 17 weight percent of the Portland cement and the excess S03 is about 6 to 24 weight percent of the Portland cement.
 22. The process of claim 17 wherein the cement is a self-stressing cement, the calcium aluminate cement is about 6 to 17 weight percent of the Portland cement and the excess S03 is about 9 to 24 weight percent of the Portland cement.
 23. The process of claim 17 wherein 2 to 8 weight percent of the cement is CaS04. 1/2 H20.
 24. The process of claim 23 wherein the calcium sulfate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the cement.
 25. The process of claim 17 wherein the Portland cement is replaced by a blended hydraulic cement selected from Portland blast furnace slag cements and Portland Pozzolan cements meeting ASTM Standard C595-68.
 26. The process for preparing a cement having controlled expansive properties consisting essentially of Portland cement clinker, calcium aluminate cement clinker in the amount from about 2 to 17 weight percent of the Portland cement clinker, and calcium sulfate to provide excess SO3 over the optimum SO3 of about 2 to 24 weight percent of the Portland cement clinker, said optimum being determined by ASTM Standard C563-70 comprising: a. determining the optimum SO3 for the Portland cement clinker, b. mixing the Portland cement clinker and calcium aluminate cement clinker with a sufficient excess of SO3 over the optimum S03 determined in step a. added as calcium sulfate to give a cement having the desired expansion level, and c. grinding the mixture to an average minimum Wagner surface of 1,600 cm2/gm.
 27. The process of claim 26 in which the calcium sulfate is added as gypsum to a maximum of about 10 weight percent of the total composition and the remainder of the calcium sulfate required to provide the determined excess of SO3 over the optimum SO3 is added as anhydrous calcium sulfate.
 28. The process of claim 26 wherein 2 to 8 weight percent of the cement is CaS04. 1/2 H2O.
 29. The process of claim 28 wherein the calcium sulfate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the cement.
 30. The process of claim 26 wherein the cement is a shrinkage-compensating cement, the calcium aluminate cement clinker is about 2 to 9 weight percent of the Portland cement clinker and the excess SO3 is about 3 to 11 weight percent of the Portland cement clinker.
 31. The process of claim 26 wherein the cement is a self-stressing cement, the calcium aluminate cement clinker is about 6 to 17 weight percent of the Portland cement clinker and the excess SO3 is about 9 to 24 weight percent of the Portland cement clinker.
 32. The process of claim 26 wherein the Portland cement clinker is replaced by a blended hydraulic cement selected from Portland blast furnace slag cements and Portland Pozzolan cements meeting ASTM Standard C595-68.
 33. An expansive cement having controlled expansive properties consisting essentially of Portland cement, calcium aluminate cement in an amount from about 2 to 17 weight percent of the Portland cement, and calcium sulfate to provide excess SO3 over the optimum SO3 of about 2 to 24 weight percent of the Portland cement, said optimum being determined by ASTM Standard C563-70.
 34. The expansive cement of claim 33 wherein the calcium sulfate is added in the form of gypsum.
 35. The expansive cement of clAim 33 wherein about 2 to 8 weight percent of the cement is CaS04. 1/2 H2O.
 36. The expansive cement of claim 35 wherein the calcium sulfate present in hemihydrate form is no greater than 60 percent of the total calcium sulfate in the cement.
 37. The expansive cement of claim 33 wherein said cement is a shrinkage-compensating cement, the calcium aluminate cement is about 2 to 9 weight percent of the Portland cement and the excess SO3 is about 3 to 11 weight percent of the Portland cement.
 38. The expansive cement of claim 33 wherein said cement is a self-stressing cement, the calcium aluminate cement is about 3.5 to 17 weight percent of the Portland cement and the excess SO3 is about 6 to 24 weight percent of the Portland cement.
 39. The expansive cement of claim 33 wherein said cement is a self-stressing cement, the calcium aluminate cement is about 6 to 17 weight percent of the Portland cement and the excess SO3 is about 9 to 24 weight percent of the Portland cement.
 40. The expansive cement of claim 33 wherein the Portland cement is replaced by a blended hydraulic cement selected from Portland blast furnace slag cements and Portland Pozzolan cements meeting ASTM Standard C595-68. 